It would, therefore, greatly interfere with the useful work of those organisms normally present if we permitted the formation of enormous quantities of bacteria, especially of such as are harmful to us; so we must endeavor to eliminate them and not give them the opportunity to turn against us, and we must do all in our power to keep the peristalsis of the bowels in good working order so as to prevent any stagnation of their contents, as such a stagnation, in addition to favoring the growth of bacteria, also facilitates the development of auto-intoxication. Even if it is true that most of the end-products of proteid food in our intestines, like indol and skatol, are not able to produce severe poisoning if injected into other animals; still there is no doubt that in medical practice not infrequently cases are observed where the retention of all these products together results in very grave conditions. Thus Ewald[212] has published the case of a woman who, for about a month, retained the contents of the bowels and in consequence presented a serious condition of intoxication; after eliminating a large quantity of fæces—pitch dark—she recovered and the symptoms of intoxication disappeared. Senator also published a very interesting case of auto-intoxication with hydrothionuria. Footnote 212: Ewald: “Die auto-intoxication,” Berl. klin. Wochenschr., No. 7-8, 1900. We often have occasion to note cases of persons having no bowel action for two to three days, who then complain of headache, loss of appetite, and various nervous symptoms, neurasthenia, etc., all of which may, perhaps, be regarded as of reflex origin; but when we see in such people a yellow or yellowish-gray complexion which, after a good purge, resumes its clear condition, clinically, we regard it as auto-intoxication. Even if, as already mentioned, most of the elements of albuminous catabolism are not toxic if injected into animals, still, occasionally, toxic products can be formed, such as cholin and neurin, which come from the former. These elements arise from decomposition of the lecithin, which, of our various foodstuffs, is contained in the greatest quantity in eggs; and these substances can provoke serious nervous symptoms. In such cases there is, of course, a stagnation of long duration of the bowels, but such a condition as the latter can arise without a stricture or obstruction, although these are the most frequent causes. Another toxic product is the pepto-toxin of Brieger.